Treatment of clays



United States Patent TREATMENT OF CLAYS William E. Brown, Gibsonia, Pa.,assiguor to Gulf Research & Development Company, Pittsburgh, Pa., acorporation of Delaware No Drawing. Application November 18, 1954,Serial No. 469,854

28 Claims. (Cl. 252-855) This invention relates to a process of treatingbodies comprised wholly or in part of clays, including clay-likematerials, for the purpose of maintaining and/or restoring thepermeability to fluids of such bodies and rendering them stable towarddisruption by mechanical and/or chemical forces. More particularly, thisinvention relates to a process of treating bodies comprised wholly or inpart of clays, including clay-like materials, subject to swelling and/ordispersion, with subsequent loss of permeability and reduction inmechanical strength, for the purpose of maintaining and/ or restoringthe permeability to fluids of such bodies and rendering them stabletoward disruption by mechanical and/ or chemical forces.

Clay-containing bodies often are substantially impermeable or have a lowpermeability to fluids or lose some or all of the permeability they maypossess when they are subjected to the action of liquids such as water,certain brines, emulsions containing water or certain brines, etc.Treatment of such clay bodies in accordance with the process of thisinvention will render them permeable, prevent a reduction in fluidpermeability and/or restore fluid permeability to those clay bodies inwhich it has been lost. As a result of the treatment the resistance ofthe clay bodies to mechanical and/or chemical disintegration will alsobe substantially increased.

The clay or clay-like materials which can be treated in accordance withmy invention can include any natural geologic formations or artificialformations such as railroad or highway embankments, road beds and roadsurfaces, automobile parking areas, areas for outdoor sports, storageareas, military installations, etc. Included also among the materialswhich can be treated to improve or maintain their permeability and theirphysical and/ or chemical stability are manufactured articles containingclays or clay-like materials. As an example, but without being limitedthereto, this process can be employed to treat articles cast, extrudedor otherwise formed from clay to increase their mechanical strengthprior to and/ or after firing.

The process of this invention has particular applicability in thetreatment of natural geologic formations for the purpose of preventingor correcting the loss in permeability thereof caused by swelling and/ordispersing of the clay contained therein, preserving the approximategeometry of the grains of the formation, maintaining the poredistribution of the formation and firming the formation if it isuncemented or poorly cemented. More specifically, this invention isespecially advantageous in the treatment of a clay-containing formationadjacent a borehole in wells in order to increase, maintain and/ orrestore I the permeability of the formation by rendering the claycontained therein resistant to swelling, disruption and/ or migration,and also to shrink essentially irreversibly the hydrated, swollen claywhich may be present in said formations adjacent wells producing fluids,such as hydrocarbons, water, etc., or in wells which are used to injectsuch fluids into a geologic formation. The clay in the Hoe 2formationcan be that which was present originally, or it can be claywhich was introduced into the formation in the process of creating theborehole, e. g., by the use of a clay-containing drilling mud, or insubsequent operations.

The clay originally present in the formation can reduce the permeabilityof the formation by swelling and/or migrating to form bridges or blocksin the pores of the formation or in perforations in casing, screens,etc., used in well completions, as a result of contact of said clay withaqueous liquids such as water, certain brines, emulsions containingwater or certain brines, etc. This liquid can be introduced into theformation as drilling mud filtrate, injection water, water from leaks inor behind the casing, or ground water associated with the formation. Of:particular concern in the case of introduced clay is that day which, asa component of the drilling mud, invades the formation during thedrilling of the borehole. High swelling montmorillonite is often used indrilling muds, among other reasons, because of its ability 'to create alow permeability filter cake on the formation. Under some conditions, alow permeability zone is created within the formation in the vincity ofthe borehole from invasion by the drilling mud. In addition, if the mudfilter cake is not removed completely when drilling has been completed,it forms a barrier to the flow of fluid into or outfrorn the formation.The invention disclosed and claimed herein will shrink the hydrated,swollen clay in the formation, mud cake, and/0r invaded zone so as tosubstantially increase the permeability and mechanical and chemicalstability of the formation.

Among the clays which may be present originally in natural geologicalformations or may have been int-'r'oduced therein and which can beeffectively treated in accordance with the present invention there areincluded clay minerals of the montmorillonite group such asmontmorillonite, saponite, nontronite, he'ctorite, and sailconite; thekaolin group such as kaolinite, nacrite, dic'kite, and halloysite; thehydrous-mica group such as hydrobiotite, glauconite, illite andbramallite; the chlorite group such as chlorite and chamosite; clayminerals not belonging to the above groups such as vermiculite,attapulgite, and sepiolite; and mixed-layer varieties of the aboveminerals and groups. The clay content of the formations can be comprisedsubstantially of a single species-of clay mineral, or of severalspecies, including the mixed-layer types of clay. Of the clay mineralscommonly encountered, in the drillingof wells in natural geologicalformations which can be productive of the difliculties herein noted andwhich can be treated effectively in accordance with the presentinvention are clay minerals selected from theclass consisting ofthemontmorillonite group, hydrous-mica group, chlorite group, and kaolingroup. It will be understood that the clay formations treated inaccordance with the invention need not be composed entirely of clay butmay contain other mineral components associated therewith.

Clays can swell and/or disperse, disintegrate or otherpand and bedisrupted to the extent that they will .bei come unconsolidated and moveinto a borehole. Formations which consist largely of clay can developpressures on the order of several thousand pounds per square inch uponabsorbing water in a confined space.

The clay materials defined above occur as minute, platelike, tube-likeand/or fiber-like particles having an extremely large surface areacompared to that of an equivalent quantity of a granular material suchas sand. This combination of small size and great surface area resultsin a high surface energy with attendant unusual surface properties andextreme affinity for surface-active agents. The structure of some ofthese clays, as for instance montmorillonite, can be pictured as a stackof sheet-like three-layer lattice units which are weakly bonded to eachother and which are expanded in the c crystallographic direction bywater or other substances which can penetrate between the sheets andseparate them.

All clay minerals have ion-exchange properties. Thus, for example,montmorillonite has a cation-exchange capacity of from about 90 to 130milliequivalents per 100 grams of pure clay, illite from about 20 to 40milliequivalents, and kaolinite from about 5 to 15 milliequivalents.Under ordinary oil-well conditions the ion-exchange reactions betweenthe clays and substances as sociated with the clays and capable ofreacting therewith are essentially reversible.

The properties of the clays vary widely with the cations occupying thebase-exchange positions or sites. A baseexchange position or site can bedefined as an area, in this instance on a clay crystal, which hasassociated with it an exchangeable cation. Among the cations which aregenerally found on the base-exchange position or site can be mentionedsodium, potassium, calcium, magnesium, iron, hydrogen, etc. Thesecations are believed to be held to the clay surface by ionic forces.

The cations occupying the base-exchange sites on the clay can be thoseoriginally present or cations finding their way to the base-exchangeposition from the liquids in contact therewith. Accordingly, the natureand concentrations of ions in the water in contact with the clay candetermine the cations occupying the base-exchange sites. In most oilwell formations, the natural waters associated therewith contain sodiumas the predominant cation, with calcium, magnesium and other cationspresent in much smaller quantities. Since the base-exchange positions onthe clay are occupied by cations, in many cases the cation will besodium when natural ground waters such as those described above areassociated therewith. Unfortunately, however, as for example in the caseof the sodium form of montmorillonite, these clay minerals swell in thepresence of water or certain brines and can, in some instances, exertpressures up to thousands of pounds per square inch. Thus, dependentupon the amount of water absorbed, the clay can change to a rigid pasteor a gelatinous mass, or if sufficient water is present, the clay candisperse completely into the aqueous phase.

I have found that the difficulties noted above can be substantiallyreduced and a clay body can be stabilized to impart or maintainsatisfactory permeability to fluids, improved mechanical strength andincreased resistance to chemical attack by treating such clay body withsubstituted ammonium ions, derived from aliphatic nitrogen compounds,selected from the group consisting of di-alkylsubstituted ammonium ionswherein each alkyl substituent has a total of 3 to 8 carbon atoms, withthe longest straight chain, starting with the carbon attached to thenitrogen, having 3 to 7 carbon atoms, preferably 3 to 6 carbon atoms;tri-alkyl-substituted ammonium ions wherein each alkyl substituent has atotal of 3 to 8 carbon atoms, with the longest straight chain, startingwith the carbon attached to the nitrogen, having 3 to 7 carbon atoms,preferably 3 to 6 carbon atoms; and tetra-alkylsubstituted ammonium ionswherein each alkyl substituent has a total of 2 to 8 carbon atoms, withthe longest straight chain, starting with the carbon attached to thenitrogen, having 2 to 7 carbon atoms, preferably 3 to 6 carbon atoms.The di-alkyl, tri-alkyl and tetra-alkyl ammonium ions can be symmetricalor unsymmetrical.

While the substituted ammonium ions defined above are effectiveclay-stabilizing agents, the parent basic nitrogen compounds from whichthe substituted ammonium ions are derived have essentially noclay-stabilizing action. Di-, tri-, and tetra-substituted ammonium ionshaving alkyl substituents of 8 or more carbon atoms in a straight chainform clay complexes which can swell or disperse in organic liquids, thisproperty being more pronounced the greater the length of the alkylchain. They are thus of limited utility in stabilizing clay bodies whichmay come in contact with organic liquids. Di-, tri-, andtetrasubstituted ammonium ions having alkyl substituents with 8 or morecarbon atoms in a straight chain tend to produce an increase in clayvolume in forming a clay complex which may result in swelling ofunhydrated clay and only little or no shrinking of hydrated swollenclay.

The substituted ammonium ions can be obtained, among other ways, fromsalts prepared by reacting an appropriate basic nitrogen compound of theclass described with an acid, preferably one whose anionic componentwill not form a precipitate with ions associated with substances such asaqueous fluids with which the substituted ammonium salt may come incontact. Thus, if the fluids contain a significant concentration ofalkaline earth ions, it is inadvisable to employ salts whose anionic component may be sulfate, oxalate, etc., since a precipitate can result.Among the compounds which can be employed in preparing the salts arehydrochloric acid, hydrobromic acid, nitric acid, lactic acid, citricacid, salicylic acid, etc., lower fatty acids such as formic, acetic,propionic, etc., and propyl bromide, ethyl bromide, isopropyl iodide,etc. Among the salts which are satisfactory for use in accordance withthe present invention are di-npropylammonium chloride,di-n-propylammonium acetate, di-n-propylammonium citrate,n-propyl-n-butylammonium chloride, di-n-butylammonium chloride,di-nbutylammonium acetate, di-n-butylammonium lactate, din-butylammoniumproprionate, diisobutylammonium chlo ride, diisobutylammonium formate,diisobutylammonium salicylate, di-n-arnylammonium chloride,diisoamylammonium chloride, di-Z-methylbutylammonium chloride, di nhexylarnmonium chloride, di n heptylammo nium chloride, di nheptylammonium acetate, trin propylammonium chloride, tri npropylammonium iodide, tri-n-butylammonium chloride,tri-n-butylamrnoniurn acetate, tri-n-butylammonium nitrate,triisobutylammonium chloride, tri-n-amylammonium chloride,triisoamylammonium chloride, tri-n-hexylammonium chloride,tri-n-heptylammonium chloride, tetraethylammonium chloride,tetraethylammonium bromide, tetra-npropylammonium chloride,tetra-n-butylammonium chloride, tetra-n-butylammonium iodide,tetra-n-butylammonium acetate, tetraisobutylammoniurn chloride,tri-nbutyl-3-methylbutylammonium iodide, tetraisoamylammonium chloride,tetraisoamylammonium iodide, tetran-hexylammonium chloride, andtetra-n-heptylammonium chloride.

In treating the clay, substituted ammonium ions or mixtures of thesubstituted ammonium ions dissolved in any suitable polar solvent suchas water, methyl alcohol, ethyl alcohol, mixed solvents, etc. can beemployed. The solution employed can be of any desired concentration,from as little as one-hundredth molar to a saturated solution, butpreferably in a concentration of about 0.75 to about one and one-halfmolar.

The amount of solution necessary to treat the clay body and obtain thebeneficial results of this invention depends on a number of variables,for example the amount of clay, the concentration of the treatingsolution, the porosity of the clay body, the desired depth ofpenetration into the clay body and the type of clay to be treated. Ingeneral, the clay is contacted with solutionsof substituted ammoniumions in such amounts as to provide at least 1, and preferably at least5, milliequivalents of substituted ammonium ions per milliequivalent ofbase-exchange capacity of the clay. In any case, best results areobtained by using an excess of substituted ammonium ions, measured asmilliequivalents, over the number of baseexchange positions, alsomeasured as milliequivalents, on

the clay to betreated.

To treat the clay with the solution containing the substituted ammoniumions any suitable method that will assure effective contact between thesolution and the clay can be employed. In treating a formation adjacenta well, for example, the solution containing the substituted ammoniumions can be spotted adjacent the formation or formations to be treatedand then be permitted to permeate the formation, pressure being used toforce the solution into the formation if desired. In addition, thesolution can be used to treat an oil well formation by spotting, priorto shooting, a sufficient amount of the solution in a well bore adjacenta section to be shot and then shooting. Also, in gun perforating or jetperforating a well, the solution can be spotted through the interval tobe perforated and the gun then inserted and fired in the hole oppositethe interval. In secondary recovery, such as a water flood program, thetreating solution can be used in front of the flood to stabilize theclay in the formation as the flood progresses through the formation,thus precluding a drop in injection rate caused by reduced permeabilitydue to swelling and/or dispersing of the clay. In treating the formationadjacent a borehole of a well which is producing hydrocarbons, thebeneficial results of this invention can be obtained by treating theformation with sufiicient of the treating fluid to obtain a penetrationof at least one foot and preferably between about 5 and 50 feet, andthen returning the well to production.

The mechanism involved in treating clays in accordance with my inventionis an ion-exchange reaction between exchangeable cations of the clay andthe substituted ammonium ions in the treating solution. When the clay iscontacted with the substituted ammonium ions identified above, thesubstituted ammonium ions exchange quickly and in an essentiallyirreversible manner with the cations occupying the base-exchange siteson the clay structure. As a result of this treatment, hydrated, swollenclay will shrink essentially irreversibly, unhydrated clay will berendered insensitive to water and other swelling agents, and theresistance of the clay to mechanical and chemical attack will beincreased.

In order to demonstrate the effectiveness of the substituted ammoniumions identified above as clay-stabilizing agents, I have run a series oftests in which various substituted ammonium ions were employed. Thesubstituted ammonium ions were formed by dissolving in water saltsobtained by the reaction of the basic aliphatic nitrogen compound with ahalogen acid. Montrnorillonite was chosen as the clay for these testsbecause of its very high ability to swell and disperse. The testscomprised placing 0.077 gram of montmorillonite (0.077 milliequivallentbase-exchange capacity) suspended in 5.0 milliliters of a salt solutionin a test tube. One liter of the salt solution prior to suspendingmontmorillonite therein contained 2,317 milligrams of sodiumbicarbonate, 279.9 milligrams of calcium chloride hydrate, 434.2milligrams of magnesium chloride hydrate, and 0.86 milligram ofmagnesium sulfate. The contents of the test tube were allowed to set for48 hours, after which the amount of precipitate was measured. Thesubstituted ammonium ion was then added to the contents of the test tubein an amount equal to five times the baseexchange capacity of the clayand the mixture was shaken for minutes and subsequently allowed to standfor 24 hours. At the end of this period the volume of clay precipitatewas estimated and such quantity of supernatant liquid was withdrawn fromthe test tube that the volume of the liquid and clay remaining was thesame as the volume of the clay suspension originally treated. Fifteenmilliliters of distilled water were added to the resulting mixture andthe test tube was shaken for 15 minutes and allowed to stand for 24hours, after which the volume of clay precipitate was again estimated.This cycle was repeated a number of times. At about the 15th test cycleand for one cycle only, a salt solution similar to that in which themontmorillonite was initially dispersed was substituted for thedistilled water. Otherwise, the procedure was not changed. Each cycleresults in a decrease in the salt concentration of the aqueous solutionand the concentration of treating agent in equilibrium with the clayprecipitate. This dilution process will cause swelling and/or dispersionof the clay if it has not been effectively stabilized. The substitutionof the original Table I Compound Cycles to Cycles to Colloidal SwellingAppearand/or ance Dispersion Methylammonium chloride 3 10 Ethylammoniumchloride-. 6 6 n-propylammonium chloride-. 3 14 Isopropylammoniuinchloride. 3 7 n-butylammonium chloride. 7 10 Isobutylammonium chloride.2 4 sec-butylammonium chloride. 3 l1 t-butylammonium chloride 1 5n-arnylammonium ehlorid 17 21 Isoamylammonium chlori 4 14n-hexylammonium chloride. 17 a n-heptylammonium chloride 17 a2-ethylhexylammonium chloride 17 a 1,1,3,3-tetramethyl-n-butylammoniumride a n-nonylammonium chloride. a Dodecylamrnouium chloride-- aTridecylammonium chloride. 2 Tetradecylammonium chloride-. an-octadecylammonium chloride. 4 Ethanolammonium chloride 33-methoxypropylammonium chloride 18 l-methylbutylammonium chloride. 18Aliylammonium chloride 4 1,3-dimethylbutylammonium chloride. 18Dimethylammonium chloride 10 Methylethylammonium chloride. 18Diethylammonium chloride 16 Ethyl-n-propylammonium chloride.Ethylisopropylammonium chloride. Diisopropylammonium chloride.--Di-n-propylammonium chloride--. n-propyl-n-butylammonium chloride.D-n-butylammonium chloride...-- Diisobutylammonium chloride-.Din-amylammonium chloride. Diisoamylammonium chlorideDi-2-methylbutylammonium chloride.. Di-n-hexylammonium chlorideDi-n-heptylammonium chlorid Diethanolammonium chloride Trimethylammoniumchloride. Triethylammonium chloride- 2-chloroethyldiethylammonium chl2-ohlor-n-propyldiethylammonium chlo Tri-n-propylammonium chlorideTri-n-butylammonium chloride. Triisobutylammonium chloride-Tri-n-amylammonium chloride... Triisoamylammonium chloride..-Tri-n-hexylammonium chloride. Tri-n-heptylammonium chloride N,N-diethyldodecylammonium chloride. Triethanolammonium chloride'Dimethylethanolammonium chloride. Tetramethylammonium chlorideTetramethylammonium bromide-.. Tetramethylammonium iodide'letraethylammonium chloride..- Tetraethylammonium bromide--...Tetra-n-propylammonium chloride..- Tetra-n-butylammoniu1n ehlorideTetra-n-butylammonium iodide Tetraisobutylammonium chlorideTri-n-butyl-3-methylbutylammonium iodide-. Tetraisoamylammonium chloridei 7 Table I.Continued denotes that the test was discontinued. at the endof 24 cycles and no swelling, dispersion, or colloidal appearance wasnoted.

(a) denotes that the test, had a colloidal appearance at the cycleindicated in column -A"but had not swelled or dispersedat the end of 24cycles.

In the above table, by colloidal appearance it is meant that afterstanding 24 hours the supernatant liquid retains a turbid or opalescentappearance characteristic of that caused'by the scattering of incidentlight by suspended colloidal particles. The appearance. of such'acolliodal, condition indicates that the clay has not been stabilized.

by the substituted ammonium ion tested. By swelling the above volume offormation, an excess over the theoretical quantity is employed to assurerapid and com plete reaction with the clay. The treating solution isintroduced through a string of small diameter pipelowered to within afew feet of the bottom of the hole and allowed to flow in by gravity.Since the treating solution has a much higher specific gravity'thanwater, oil or ordinary oil-field brines, it will displace water or oilopposite the formation to be treated and will then flow into theformation. As an aid in displacing the treating solution into theformation, pressure can be employed. The treating solution is introducedinto the formation slowly and allowed to remain in contact with thefor-,

mation for about 24 hours, after which the unused portion, along withproduced fluid, is withdrawn from the well.

hole can be treated in accordance with the invention by setting a bridgeplug,

tom ofthe'formation to betreated, and thereafter proceeding as describedabove considering thetop of the I bridge plug to be the bottom of theborehole.

his meant that thesettledvolume of the clay at the end I of 24 hours isat least 1 /2 times the settled volume of the clay at the beginning-ofthe test. By dispersion it ismeant that the clay is dispersed. uniformlythroughout.

the liquid so that at the end of 24 hours no precipitateor sediment canbe detected. Obviously, when the clay swells or ldisperses it has notbeen stabilized by the pare ticular substituted ammonium ion tested.

The above table graphically illustrates the advantages of the presentinvention. Thus, it can be seen that monosubstituted ammonium ionsderived from aliphatic nitrogen bases, 'e; methylammonium chloride,n-propylammonium chloride, n-butylammonium chloride, isoamylammoniumchloride, etc.; diand tri-substituted ammonium ions derived fromaliphatic nitrogen bases having substituent groups of less than 3 carbonatoms, e. g., dimethylammonium chloride, diethylammonium chloride,trimethylammonium chloride and triethylammonium chloride; andsubstituted ammonium ions derived from aliphatic nitrogen compounds inwhich the substituent groups contain a hydrophilic portion, e. g.,ethanolammonium chloride, diethanolammonium chloride, andtriethanolammonium chloride, are unsatisfactory as treating agents forstabilizing clays, for clays treated therewith were easily dispersed andresulted in aqueoussolutions having a colloidal appearance. As shown inthe table, diand tri-substituted ammonium ions derived from aliphaticnitrogen compounds having 3 to 7 carbon atoms in each straight chain, asWell as tetra-substituted ammonium ions having from 2 to 7 carbon atomsin each straight chain, proved to be very effective, for even at the endof 24 cycles the clay treated therewith was unaffected by water or thesalt solution.

There follow illustrative embodiments of the actual practice of theprocess of this invention as applied to oil wells producing fromformations containing clay. It is understood that the proceduresdescribed are illustrative and the invention is not to be limitedthereby.

In treating a formation adjacent the bottom of a borehole to stabilizethe clay, said formation containing about 5 per cent by weight ofmontmorillonite and having a porosity of about 15 per cent, so as toattain a radial depth of treatment of at least 5 feet from the borehole,about 150 gallons of a one-molar aqueous solution of substitutedammonium ions derived from trin-propylammonium chloride for each foot ofvertical thickness of the formation to be treated is used. Whiletheoretically only about 70 gallons of the above treating solution wouldbe needed to react with all of the clay in Such operations are oftendeveloped in what is termed a five-spot pattern, with the producing welllocated in the corners.

The process of this invention is also used to advanrage in secondaryrecovery operations wherein a displacement fluid such as water isapplied undcrpressure to an oil-bearing. formation by means of speciallyequippedinput wells penetrating said formation for the purpose offorcing the oil out of theoil-bearing formation through an output wellpenetrating said formation.

center of a square formed by water input wells at the four Byintroducing any of the treating solutions disclosed herein into thewater input wells prior to injection of water, the treating solutionwill move ahead of the advancing water and thus stabilize the clay inthe formation before the clay has .had an opportunity to come in contactwith the injection Water and be deleteriously affected by contacttherewith. In actual practice, the treating solution is placed adjacentthe formation to be treated by introducing the same through a string ofsmall diameter pipe lowered to a point adjacent the section of theformation to be treated in the manner described in the paragraph nextpreceding and is followed by normal injection of water. To establish afront of the treating solution about five feet thick (radially) ahead ofthe injection water at a radius of about 20 feet from the borehole in aformation having the same montmorillonite content and porosity describedabove, about 650 gallons of a one-molar aqueous solution oftri-n-propylamrnonium chloride is sufiicient for each foot of thickness(vertical) of the formation to be treated. Because of prior treatment inaccordance with the invention, a satisfactory permeability of the clayduring the water flood is maintained or improved, thereby 1eading tomore eflicient recovery of the fluids to be produced.

The treating solutions herein disclosed are also employed with advantagein oil-Well perforating. When clay-water drilling mudsare used in rotarydrilling, they seal off the openings in porous formations encounteredwhile drilling. In well completions where such formations are cased offand the casing must be perforated for production, the sealing propertyof claywater muds can be detrimental. Since the hydrostatic head of themud in the borehole exceeds the formation pressure, when the casing isperforated the clay-water mud rushes into the perforated formation untila mud cake seal is established or the pressure is balanced. This oftenis accompanied by a fresh water loss to the formation, which in the clayformations described, swells the clay which is present. In addition,there often results blocking of the perforated formation to such anextent that on subsequent completion of the well the perforations Itwill be understood that, instead of treating formations adjacent thebottom of a borehole, any sel'ected formation interval above the bottomof the borein known manner, at the bot 9 have to be" washed oracidi'z'ed with reagents known as niud clean out agents.

To avoid such difliculties in perforating operations in accordance withthe present invention, :a string of tubing is lowered into the boreholeso that its lower end is adjacent the bottom of the section to betreated'and' about 300 gallons of a suitable oil-base drilling fluid isintroduced through the tubing to displace the clay-Water drilling mudupwardly in the borehole. About 150 gallons of a one-molar aqueoussolution of the treating solution, e. g., tri-n-propylammonium'chloride, for each foot of thickness of the formation is thereafterintroduced through the tubing and in turn displaces the oil-basedrilling fluid upwardly in the borehole. The perforating gun, eitherbullet er jet, is then lowered into the treating solution opposite theformation to be treated and the casing perforated in the usual manner.The hydrostatic head in the borehole exceeds the formation pressure andthus will force the treating solution into' the formation. In this way,the naturally-occurring clay, which was exposed to fresh water lost .tothe formation from the clay-water drilling fluid, will .be shrunken andstabilized and when the well is permitted to how, or is swabbed orpumped, the unused clay-stabilizing agent in the treating solution willbe produced from the formation. This operation Will leave the formationsubstantially free from plugging by mud cake or other hydrated clay.Thus, by employany ane one of the treating agents disclosed herein whileperforatingthe formation will be prevented from being mudded olf, theharmful effects of fresh water on naturally-occurring clay will benullified, the necessity for Washing perforations with so called mudacids will be eliminated, and the use of conventional clay-waterdrilling rnuds will be permitted in areas where the producing formationscontain swelling-type clays and the more expensive oil-base muds arecommonly used.

Similarly in oil well shooting in open hole with high explosives, such.as nit-roglycerine, trinitrotoluene, etc., thefre'shly exposedformation may also be contacted a clay-water drilling fluid with theaccompanying harmful effects described above. The drilling fluidopposits the tormation to be treated in such case can be replaced withan oil-base drilling fluid followed by the treating solution in themanner described above, and the rr'pltisive can be lowered into thesolution and detonated in" the customary manner. The beneficial resultsobtaiiied in employing the treating solutions of the invention whileperforating will also accompany their use with high eirplosives.

While I have found that the specific substituted ammonium ions disclosedherein or mixtures thereof are satisfactory for the purposes of thisinvention, there are certain instances wherein it is advantageous toemploy in admixture therewith other substituted ammonium ions is:specifically disclosed herein but which have sirn'ilar propertiethereto, as for example, the substituted ammo'nium ions disclosed in mycopending application filed concurrently herewith, application SerialNo. 469,862,

as well as in the other concurrently filed applications filed jointlywith Clifford R. Giacobine, application "Serial Nos.

469,85 to 469,861, inclusive. For eXample, although by far the greatest:portion of the base-exchange sites on a clay mineral surface will havean area approximating the average area per exchange site, a small numberof sites will have an area considerably less than the average. Becauseof the spatial configuration of their hydrophobic par-t, certainsubstituted ammonium ions will not be able to occupy these smallersites, in which case it is advantageous to use one or more additionalsubstituted ammonium ions of different spatial configuration which canoccupy the remaining positions and thus complete the stabilizationreaction. It is believed that this use is especially advantageous in thecase of the mixed-layer 'clayminerals.

Obviously, many modifications and variations of the ini6 vention, ashereinabove set forth, may be made without departing from the spirit andscope thereof, and there'- fore only such limitations should be imposedas are indica-ted in theappended claims.

1.- A method of stabilizing a clay-containing body which comprisescontacting such clay-containing body with substituted ammonium ions,derived from aliphatic nitrogen compounds, selected from the groupconsisting of di-alkyl-substituted ammonium ions wherein each alkylsubstituent has a total of 3 to 8 carbon atoms, with the longeststraight chain, starting with the carbon. attached to the nitrogen,having 3 to 7 carbon atoms; t-rialkyl-substituted ammonium ions whereineach alkyl substituent has a total of 3 to 8 carbon atoms, with thelongest straight chain, starting with the carbon attached .to thenitrogen, having 3 to 7 carbon atoms; and tetraalkylesubstitutedammonium ions wherein each alkyl substituent has a total of 2 to 8carbon atoms, withthe longest straight chain, starting with the carbonattached to the nitrogen, having 2 to 7 carbon atoms.

'2. A method of stabilizing a clay-containing body as in claim 1, inwhich the clay-containing body comprises at least one clay mineralselected from the class consisting of the montmorillonite group, hydrousmica group, chlorite group and kaolin group.

3. A method -.of stabilizing a clay-containing body which comprisescontacting such clay-containing body with di-alkyl-substituted ammoniumions wherein each alkyl substituent has a total of 3 to 8 carbon atoms,with the longest straight chain, starting with the carbon attached .tothe nitrogen, having 3 to 7 carbon atoms.

4. A method of stabilizing a clay-containing body which comprisescontacting such clay-containing body with trialkyl-substituted ammoniumions wherein each alkyl substituent has a total of 3 to 8 carbon atoms,with the longest straight chain, starting with the carbon attached tothe nitrogen, having 3 to 7 carbon atoms.

5. A method of stabilizing a clay-containing body which comprisescontacting such clay-containing body with tetra-alkyl-substitutedammonium ions wherein each alkyl substituent has a total of 2 to 8carbon atoms, with the longest straight chain, starting with the carbonattached to the nitrogen, having 2 to 7 carbon atoms.

6. A method of stabilizing a clay-containing body which comprisescontacting such clay-containing body with substituted ammonium ionsderived from tri-n-propylamine.

7. A method of stabilizing a clay-containing body'which comprises acontacting such clay-containing body with substituted ammonium ionsderived from tri-n-butylamine.

8. A method of stabilizing a clay-containing body which comprisescontacting such clay-containing body with tetran-hexylammonium ions.

9. A method of stabilizing a clay-containing body which I comprisescontacting such clay-containing body with substituted ammonium ionsderived from tri-n-amylamine. 10. A method of stabilizing aclay-containing body which comprises contacting such clay-containingbody with substituted ammonium ions derived from di-n-butylamine. 11. Amethod of stabilizing a clay-containing formation adjacent a well borewhich comprises contacting such clay-containing formation withsubstituted ammonium ions, derived from aliphatic nitrogen compounds,selected from the group consisting of di-alkyl-substituted ammonium ionswherein each alkyl substituent has a total of 3 to 8 carbon atoms, withthe longest straight chain, starting with the carbon attached to thenitrogen, having 3 to 7 carbon atoms; tri-alkyl-substituted ammoniumions wherein each alkyl substituent has a total of 3 m8 carbon atoms,with the longest straight chain, starting with the carbon attached tothe nitrogen, having 3 to 7 carbon atoms; and tetra-alkyl-substitutedammonium ions wherein each alkyl substituent has a total of 2 to 8carbon atoms, with the longest straight chain, starting with the carbonattached to the nitrogen, having 2 to 7 carbon atoms.

11 12. A method of stabilizing a clay-containing formation adjacent awell bore which comprises contacting such clay-containing formation withdi-alkyl-substituted ammonium ions wherein each alkyl substituent has atotal of 3 to 8 carbon atoms, with the longest straight chain, startingwith the carbon attached to the nitrogen, having 3 to 7 carbon atoms. tit 13. A method of stabilizing a clay-containing formation adjacent awell bore which comprises contacting such clay-containing formationwith,tri-alkyl-substituted ammonium ions wherein each alkyl substituenthas a total of 3 to 8 carbon atoms, with the longest straight chain,starting with the carbon attached to the nitrogen, having 3 to 7 carbonatoms.

14. A method of stabilizing a clay-containing formation adjacent a wellbore which comprises contacting such clay-containing formation withtetra-alkyl-substituted ammonium ions wherein each alkyl substituent hasa total of 2 to 8 carbon atoms, with the longest straight chain,starting with the carbon attached to the nitrogen, having 2 to 7 carbonatoms.

15. A method of stabilizing a clay-containing formation adjacent a wellbore which comprises contacting such clay-containing formation withsubstituted ammonium ions derived from tri-n-propylamine.

16. A method of stabilizing a clay-containing formation adjacent a wellbore which comprises contacting such clay-containing formation withsubstituted ammonium ions derived from tri'n-butylamine.

17. A method of stabilizing a clay-containing formation adjacent a wellbore which comprises contacting such clay-containing formation with atetra-n-hexylammonium ions.

18. A method of stabilizing a clay-containing formation adjacent a wellbore which comprises contacting such clay-containing formation withsubstituted ammonium ions derived from tri-n-amylamine.

19. A method of stabilizing a clay-containing formation adjacent a wellbore which comprises contacting such clay-containing formation withsubstituted ammonium ions derived from di-n-butylamine.

20. A method of recovering oil from an oil-bearing formation containingclay, wherein a displacement fluid under pressure is applied to saidformation through at least one input well penetrating said formation,and wherein oil is recovered from an output well penetrating saidformation, which comprises introducing a treating solution containingsubstituted ammonium ions, derived from aliphatic nitrogen compounds,selected from the group consisting of di-alkyl-substituted ammonium ionswherein each alkyl substituent has a total of 3 to 8 carbon atoms, withthe longest straight chain, starting with the carbon attached to thenitrogen, having 3 to 7 carbon atoms; tri-alkyl-substituted ammoniumions wherein each alkyl substituent has a total of 3 to 8 carbon atoms,with the longest straight chain, starting with the carbon attached tothe nitrogen, having 3 to 7 carbon atoms; and tetraalkyl-substitutedammonium ions wherein each alkyl substituent has a total of 2 to 8carbon atoms, with the longest straight chain, starting with the carbonattached to the nitrogen, having 2 to 7 carbon atoms, into said inputwell, thereafter introducing said displacement fluid under pressure intosaid input well, forcing said treating solution through said formationby means of said displacement fluid, and recovering oil from said outputwell.

21. A method ofrecovering oil from an oil-bearing formation containingclay, wherein a displacement fluid under pressure is applied to saidformation through at least one input well penetrating said formation,and wherein oil is recovered from an output well penetrating saidformation, which comprises introducing a treating solution containingdi-alkyl-substituted ammonium ions wherein each alkyl substituent has atotal of 3 to 8 carbon atoms, with the longest straight chain, startingwith the 12 carbon attached to the nitrogen, having 3 to 7 carbonatoms,into said input well, thereafter introducing said displacementfluid under pressure into said input well, forcing said treatingsolution through said formation by means of said displacement fluid andrecovering oil from said output well.

22. A method of recovering oil from an oil-bearing formation containingclay, wherein a displacement fluid under pressure is applied to saidformation through at least one input well penetrating said formation,and wherein oil is recovered from an output well penetrating saidformation, which comprises introducing a treating solution containingtri-alkyl-substituted ammonium ions wherein each alkyl substituent has atotal of 3 to 8 carbonatoms, with the longest straight chain, startingwith the carbon attached to the nitrogen, having 3 to 7 carbon atoms,into said input well, thereafter introducing said displacement fluidunder pressure into said input well, forcing said treating solutionthrough said formation by means of said displacement fluid, andrecovering oil from said output well.

23. A method of recovering oil from an oil-bearing formation containingclay, wherein a displacement fluid under pressure is applied to saidformation through at least one input well penetrating said formation,and wherein oil is recovered from an output well penetrating saidformation, which comprises introducing a treating solution containingtetra-alkyl-substituted ammonium ions wherein each alkyl substituent hasa total of 2 to 8 carbon atoms, with the longest straight chain,starting with the carbon attached to the nitrogen, having 2 to 7 carbonatoms, into said input well, thereafter introducing said displacementfluid under pressure into said input well, forcing said treatingsolution through said formation by means of said displacement fluid, andrecovering oil from said output well.

24. A method of recovering oil from an oil-bearing formation containingclay, wherein a displacement fluid under pressure is applied to saidformation through at least one input well penetrating said formation,and wherein oil is recovered from an output well penetrating saidformation, which comprises introducing a treating solution containingsubstituted ammonium ions derived from tri-n-propylamine, into saidinput well, thereafter introducing said displacement fluid underpressure into said input well, forcing said treating solution throughsaid formation by means of said displacement fluid, and recovering oilfrom said output well.

25. A method of recovering oil from an oil-bearing formation containingclay, wherein a displacement fluid under pressure is applied to saidformation through at least one input well penetrating said formation,and wherein oil is recovered from an output well penetrating saidformation, which comprises introducing a treating solution containingsubstituted ammonium ions derived from tri-n-butylamine, into said inputwell, thereafter introducing said displacement fluid under pressure intosaid input well, forcing said treating solution through said formationby means of said displacement fluid, and recovering oil from said outputwell.

26. A method of recovering oil from an oil-bearing formation containingclay, wherein a displacement fluid under pressure is applied to saidformation through at least one input well penetrating said formation,and wherein oil is recovered from an output well penetrating saidformation, which comprises introducing a treating solution containingtetra-n-hexylammonium ions, into said input well, thereafter introducingsaid displacement fluid under pressure into said input well, forcingsaid treating solution through said formation by means of saiddisplacement fluid, and recovering oil from said output well.

27. A method of recovering oil from an oil-bearing formation containingclay, wherein a displacement fluid under pressure is applied to saidformation through at least one input well penetrating said formation,and wherein oil is recovered from an output well penetrating saidformation, which comprises introducing a treating solution containingsubstituted ammonium ions derived from tri-n-amylamine, into said inputwell, thereafter introducing said displacement fluid under pressure intosaid input well, forcing said treating solution through said formationby means of said displacement fluid, and recovering oil from said outputwell.

28. A method of recovering oil from an oil-bearing formation containingclay, wherein a displacement fluid under pressure is applied to saidformation through at least one input well penetrating said formation,and wherein oil is recovered from an output well penetrating saidformation, which comprises introducing a treating solution containingsubstituted ammonium ions derived from di-n-butylamine, into said inputwell, thereafter introducing said displacement fluid under pressure intosaid input well, forcing said treating solution through said formationby means of said displacement fluid, and recovering oil from said outputwell.

References Cited in the file of this patent UNITED STATES PATENTS LietzNov. 11, Ralston et a1. May 25, Endersby May 9, Ratcliffe Jan. 21,Albaugh Apr. 29, Bond June 7, Jordan Nov. 28, Meadors June 3, MeadorsJuly 15, Viles Aug. 19, Lytle Nov. 17, Skinner June 14,

FOREIGN PATENTS Germany July 9,

1. A METHOD OF STABILIZING A CLAY-CONTAING BODY WHICH COMPRISES CONTACTING SUCH CLAY-CONTAINING BODY WITH SUBSTITUTED AMMONIUM IONS, DERIVED FROM ALIPHATIC NITROGEN COMPOUNDS, SELECTED FROM THE GROUP CONSISTING OF DI-ALKYL-SUBSTITUTED AMMONIUM IONS WHEREIN EACH ALKYL SUBSTITUENT HAS A TOTAL OF 3 TO 8 CARBON ATOMS, WITH THE LONGEST STRAIGHT CHAIN, STARTING WITH THE CARBON ATTACHED TO THE NITROGEN, HAVING 3 TO 7 CARBON ATOMS; TRIALKYL-SUBSTITUTED AMMONIUM IONS WHEREIN EACH ALKYL SUBSTITUENT HAS A TOTAL OF 3 TO 8 CARBON ATOMS, WITH THE LONGEST STRAIGHT CHAIN, STARTING WITH THE CARBON ATTACHED TO THE NITROGEN, HAVING 3 TO 7 CARBON ATOMS; AND TETRAALKYL-SUBSTITUTED AMMONIUM IONS WHEREIN EACH ALKYL SUBSTITUENT HAS A TOTAL OF 2 TO 8 CARBON ATOMS, WITH THE LONGEST STRAIGHT CHAIN, STARTING WITH THE CARBON ATTACHED TO THE NITROGEN, HAVING 2 TO 7 CARBON ATOMS. 